Low gradient resistor



y Feb. 20, 1934. E.. G. LODGE,

LOW GRDIENT RESISTQR Filed Aug. 2s, 1951'.

la ff@ j" f 7 A v ff y C O Z7 d y C n o y; e2- L-\'-z/ 195 C i i 9i# 1 :y 22 me* df 29N/ 1 C Y T `0 Hf* (7 j! *[5 /z Patented Feb. 20, u 1934 LOW GRADIENT RESISTOR Edmund G. Lodge,

Oak Lane, Pa., assignor to Hugh H. Eby, Philadelphia, Pa. l .-Application August 26, 1931. Serial No. 559,589

Y 4 Claims. (Cl. 201-60) y My invention relates to variable resistors having perhaps their widest application in circuits of radio receiving sets, ofmicrophones and the like but adaptedto many other uses.

6 One purpose ofthe invention is to yprovide a wire-wound resistor with an ,eectiyeand novel low gradient resistance taper.' c f AV further purposeis to mount i'an electrical conducting member`r transversely across the turns 10 along a portion of a wire-wound resistor element along which it is desired to obtain a low resistance gradient.

A further purpose is to mount a. resistance wire inside or outside of the turns of a wire-wound resistor transverse to the turns along a portion lthereof at which a low resistance gradient is desired.

A further purpose is to mount a transverse resistance Wire along a portion of a wire-wound resistor at which it is desired to have a low resistance gradient with theA wire set to extend angularly with respect to the upper edge of the resistor to obtain the desired resistance gradient, `accommodating the angular setting of the wire to the size and resistance characteristics thereof and the desired low resistance gradient.

A further purpose is to determine the magnitude of a low resistance gradient along a predetermined portion of a wire-wound resistor by 30 the slope of the upper edge of a conducting sheet,

plate or the like transversely connecting windings along the said portion thereof with respect to the contacting edge of the resistor unit accommodating the slope of the transversely connecting plate to the desired resistance gradient.

Further purposes will appear in the speciilcation and in the claims.

I have elected to show a few only of the many different forms of my invention, selecting forms 40 that are practical and eilicient in operation and which well illustrate the principles involved.

Figure l indicates a resistor unit of the prior art with an exaggerated spacing between the turns and the unit shown extended or of straight extension Whereas in frequent practice it is positioned arcuately about the axis of a turn shaft mounting a contact to slide along the arcuate unit.

Figure v2 shows the structure of Figure 1 modifled along a portion of its length by having portions of the turns of the coil coated with a' low Yresistant metal such as copper to reduce the resistance of the turns in accord with an invention disclosed and claimed in a copending application, not in itself part of the present invention.

Figure. 3 is a somewhat diagrammatic view showing the unit of Figure 1 with added structure to embody one form of'the present invention giving to one portion of the coil a modified low resistance without the use of the low resistance l0 coating of Figure 2. v

Figure 4 is a view illustrating different ways of Y setting the added structure of Figure 3 to obtain selectively any one of many different low resistance gradients along a given\portion"of the coil of Figure 1 using the same added structure set diierently to accommodate different desired low resistance gradients.

Figure 5 embodies a feature disclosed in Figure 3 in combination with the modified resistor of 70 Figure 2 to obtain a lower resistance gradient than is frequently practical with the form of Figure 2.

Figure 6 is a detail modification illustrating that the structure of Figures 4 and 5 added'as a 75 transverse connecting member across the turns along a portion of the coil of Figure 1 may have any suitable form with or Without material resistance of its own and a slope with respect to the upper edge of the unit to accommodate the desired low resistance gradient.

Figures 7 and 8 are fragmentary longitudinal sections illustrating that the transverse connecting members of Figures 3' to 6 may be alternatively inside or outside of the turns.

Like numerals refer to like parts in all figures.

Describing in illustration and not in limitation and referring to the drawing The figures are intended to represent conventionally any resistors to which the invention is adapted to be applied and are all more or less diagrammatic in that the spacing between the windings lis greatly increased beyond that 'which would be usual in commercial units.

The resistors of Figures 1 and 2 may be typical 95 of the prior art, and include an insulation core 15 carrying turns 16 of suitable resistance wire.

vIn practice the resistance wire may be of extremely fine gauge, for example in radio receiving sets and loud speaker circuits oi' microphones 100 and the like, suitably 30 to 40 gauge nichrome resistance wire with some hundreds of turns to the inch.

In practice too there frequently will be a flxed terminal 17 at each end of the windingand a 105 slide contact 18 connected to an intermediate terminal, not shown, the slide contact terminal engaging the wire anywhere along the edge of the unit, that is to any one of the turns of the unit along the range of travelo! the slide.

The resistances of the individual windings of Figure 1 are the same throughout the length of the resistor while in Figure 2 these resistances have been reduced along one portion of the resistor by partially coating suitable portions of the individual turns with a low resistant metal, for example copper, the heavy lines indicating the copper-coated portions of the individual turns.

Along the contact or upper edge of the resistor all turns are as indicated at 19 desirably left uncoated, as coating at the contact surfaces of the resistor has in practice resulted in noise if the unit is used as a volume control of a loud speaker circuit, unless special precautions have been taken to avoid oxidation at the contact surfaces.

In Figure 2 along the portion 2U of the resistor, the successive individual turns are progressively tapered with respect to the length of low resistance coating and along the portion 21 thereof the turns are coated throughout their length except for the uniform short uncoated portion 19 adjacent the contact edge of the unit.

It will be seen as the slide 18 is moved along the unit to the right from the terminal 1'7 the resistance between the slide and the terminal increases in steps at the successive turns.

Along the portion 22 of the unit these steps are uniform and each equal to the resistance of a single uncoated turn.

Along the taper portion 20, Figure 2, the steps progressively lessen, the increment of resistance at the successive turns becoming smaller and smaller until when the portion 21 is reached the increment has its lowest value, the steps being low and substantially uniform along the portion 21 of the unit.

In practice it has been found that the resistance gradient corresponding to this lowest value is often higher than is desirable and one feature of the present invention permits the easy lowering of the gradient along the region 21 of the coil to any desired extent.

This may be accomplished as indicated in Figure 5 by a resistance wire 23 positioned to connect the turns along the portion 21 transversely together.

In Figure 5 the wire 23 is shown substantially parallel to the contact edge of the unit so that the increment of resistance by moving the slide contact one turn to the right is largely determined by the resistance of a small portion 24 of the auxiliary wire 23 between adjacent turns of the main winding. More strictly the increment in resistance in moving the contact slide one turn is equal to that of the portion of 23 between adjacent windings in parallel with a single turn of the main winding and the lower the resistance of the wire 23 the less will be the effect of the winding itself which is in parallel, the effect of the winding in parallel being therefore lfrequently negligibly small.

It will be seen that the larger the wire 23, the closer the spacing between the turns 16, the more perfect the contact between the individual turns and the wire 23, the smaller will be the added increment of the resistance incident to moving the Contact one turn in either direction.

While the transverse conducting wire 23 has a particular combination with the type of resistor of Figure 2 in which the low resistant gradient is partially obtained by a coating of copper or the like over a considerable portion of the individual turns, it is evident that the transverse connecting wire may be used Without any preliminary coating of the resistance turns wit copper as illustrated in Figures 3 and 4.

In Figure 3 the wire 23 includes sloping and horizontal portions respectively along the portions 20' and 21' of the unit, the resistance wire 23 transversely connecting to all the turns along its length.

The wire 23' may optionally and in many cases desirably comprise an end portion of the wire winding 16. The wire 23' is shown in Figure 3 with a strong downward slope to the right along the portion 20', and parallel to the contact edge along the portion 21 of the resistor.

This arrangement gives a range of resistance somewhat similar to that of the resistor of Figure 2, the resistance gradient being high and uniform along the portions 22 of both forms, but the tapering gradient 20 and uniform gradient 21' of Figure 3 being normally both lower than the corresponding gradients along the portions 20 and 21 of Figure 2.

It will be evident that as the contact moves one turn along the portion 20 the change in resistance is largely determined by the gradient increment 26 of one of the turns plus that of a portion 27 of the sloping wire between adjacent windings.

The greater the slope of the portion 20 the greater are the lengths 26 and 27 and therefore the steeper the resistance gradient.

It will be understood that such gradient will normally be greatly less than that along the portion 22 to the left of 20'.

Along the portion 21' where the transverse connecting wire is parallel to the contact edge of the resistor, the increment is largely determined by that of a portion 24 between the adjacent turns.

Actually there will however be a small additional increment due to imperfect contact between the turn of the resistor wire and the transverse wire.

Figure 4 illustrates that the slope of the transverse wire may be varied to obtain widely different gradients of resistance along a portion 28 with a given size of wire.

If the wire is parallel to the contact edge, as indicated in full line, the increment of resistance is largely that due to the length 24 of resistance wire between the adjacent turns.

If the wire slopes upwardly to the right, as indicated in dot at 29 there is a reduction from this value by an amount that is progressively greater with increasing slope. If the wire slopes downwardly to the right as indicated at 30 the increment of resistance corresponds to that of 20 of Figure 3.

Figure 6 illustrates that the transverse conducting member 23 may have any suitable form and a resistance of its own too low to affect the gradient.

In this event the resistance gradient along the length of the transverse connector 23 is determined by the slope of the upper edge of the conducting member with respect to the contact edge of the unit, exactly as already explained for a sloping resistance Wire.

The conducting member may in practice comprise a metal sheet or when the resistance turns are of very ne wire more suitably a low resistance metal foil.

Referring to Figure 6 it will be seen that the increment of resistance as the contact member moves to the right along the portion 28 of the resistor is determined by the slope of the upper edge of the conducting member with respect to the contact edge of the unit.

The conducting member, whether sheet or Wire, may be either inside or outside the windings as indicated respectively in Figures 8 and 7 and the conducting member may be desirably soldered to the turns at one or more points as indicated at 3l, Figure 3. 1

Where the conducting member is soldered to the windings, it is desirable to rst coat the windings with copper or the like if the resistance wire is of material that does not readily solder, such for example as nichrome.

It will be understood effective electrical contact should be maintained between the transverse conducting member and the individual turns. In practice this may be effected by clamping the unit against an insulation member as disclosed and claimed in a copending'application or in any other suitable way, either by merely clamping or by soldering or frequently desirably' by both clamping and soldering.

In view of my invention and disclosure Variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention Without copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:-

1. A wire-wound resistor coil and means for providing a low resistance gradient along a selected portion of the length of the coil and comprising a low resistance coating individual to each turn on portions of the turns along said portion of the coil and an electrical connection transversely across the turns along the said portion.

2. A wire-Wound resistor coil and means for providing a low resistance gradient along a selected portion of the length of the coil and comprising a low resistance coating individual to each turn on portions of the turns along said portion of the coil, the contact portions of the turns being left uncoated and an electrical connection transversely across the turns along the said portion,

3. A wire-wound resistor coil and means for providing a low resistance gradient along a selected portion of the length of the coil and comprising a low resistance coating individual tov each turn on portions of the turns along said portion of the coil and an electrical connection transversely across the turns along the said portion and of progressively variant distance from the contact edge of the coil.

4. A wire-wound resistor coil and means for providing a low resistance gradient along a selected portion of the length of the coil and comprising a low resistance coating on portions of the turns along said portion of the coil and an elecrical connection transversely across the turns along the said portion and soldered to the coil at spaced turns thereof.

EDMUND G. LODGE. 

